U.S. patent number 4,870,265 [Application Number 07/120,116] was granted by the patent office on 1989-09-26 for position-sensitive radiation detector.
This patent grant is currently assigned to Max-Planck Gesellschaft zur Foerderung der Wissenschaften eV. Invention is credited to Frithjof Asmussen, Thomas Schiller, Uwe Weigmann.
United States Patent |
4,870,265 |
Asmussen , et al. |
September 26, 1989 |
Position-sensitive radiation detector
Abstract
A position-sensitive radiation detector includes a substrate and
an electrically conductive electrode system which is arranged on a
surface of said substrate and the configuration and arrangement of
which permits position determination of a charge carrier beam
impinging thereon. The substrate and the electrode system each
consist of a transparent material, for example glass, or a mixture
of indium oxide and tin oxide. Disposed on the electrode system is
a layer of luminescent material. The present radiation detector
permits at the same both an electronic and an optical signal
acquisition, the latter for example photographically, visually or
by means of an optoelectronic device, such as a video camera, which
picks up the light passing through the substrate. Due to the
combined electronic and optical signal acquisition the radiation
detector can be used in a very large intensity range.
Inventors: |
Asmussen; Frithjof (Berlin,
DE), Schiller; Thomas (Berlin, DE),
Weigmann; Uwe (Berlin, DE) |
Assignee: |
Max-Planck Gesellschaft zur
Foerderung der Wissenschaften eV (Gottingen,
DE)
|
Family
ID: |
6313925 |
Appl.
No.: |
07/120,116 |
Filed: |
November 13, 1987 |
Foreign Application Priority Data
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|
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Nov 14, 1986 [DE] |
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3638893 |
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Current U.S.
Class: |
250/214.1;
250/214LA |
Current CPC
Class: |
H01J
29/10 (20130101); H01J 31/08 (20130101) |
Current International
Class: |
H01J
31/08 (20060101); H01J 29/10 (20060101); H01J
040/14 () |
Field of
Search: |
;250/213R,213VT,211R
;313/524,527,528,540 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Wedge and Strip Anodes for Centroid-Finding Position-Sensitive
Photo Nand article Detectors" Review Scientific Instruments, Jul.
1981, vol. 52, pp. 1067-1074. .
Panitz: "Video Recording of Low Intensity CEMA Images" J. Vac. Sci.
Technol., 17(3), May/Jun. 1980, pp. 757-758..
|
Primary Examiner: Nelms; David C.
Attorney, Agent or Firm: Frishauf, Holtz, Goodman &
Woodward
Claims
We claim
1. High-dynamic-range position-sensitive radiation detector
comprising
a substrate (20) and
an electrode system (18) which is disposed on a surface of the
substrate and the configuration and arrangement of which permits a
position determination of a charge carrier beam (16) impinging
thereon,
further comprising,
electro-luminescent material (22) deposited on the side of the
electrode system (18) subjected to the charge carrier beam,
and wherein
(a) the electrode system (18) consists of a transparent material;
and
(b) the substrate (20) consists of a transparent material, thereby
permitting visual observation (32, 34), through said electrode
system and substrate, of charge carrier impact on said
electro-luminescent material (22).
2. Radiation detector according to claim 1, characterized
luminescent material layer (22) covers both the electrode system
(18) and any electro-free regions of the surface of the substrate
(20).
3. Radiation detector according to claim 1, characterized by a
means (26; 34, 36) for optical detection of the optical radiation
distribution generated by charge carrier impacts on the luminescent
material layer (22).
4. Radiation according to claim 3, characterized in that the means
for optical detector include an optoelectronic means such as a
television camera (30).
5. Radiation detector according to claim 3, characterized in that
the means for optical detection includes a means (34, 36) for
visual observation of the optical radiation distribution.
6. Radiation detector according to claim 1, characterized in that
in front of the electrode system (18) a secondary electron
multiplier (14) is disposed.
7. Radiation detector according to claim 1, characterized in that
the transparent electrode arrangement consists of a mixture of
indium oxide and tin oxide.
8. Radiation detector according to claim 7, characterized in that
the ratio of indium to tin is about 20:1.
9. Radiation detector according to claim 7, characterized in that
tin oxide is present as SnO.sub.2 while the indium oxide is present
in various oxidation stages.
10. Radiation detector according to claim 1, characterized in that
the electrode arrangement comprises an electrode consisting of
resistance material.
11. Electro-optical means including a substrate (20) of an
optically transparent material and at least one optically
transparent electrode (18) which is arranged on a surface of the
substrate in a configuration which permits electrical determination
of a position of a charge carrier beam (16) including thereon, and
consists essentially of a mixture of indium oxide and tin
oxide.
12. Means according to claim 11, characterized in that the ratio of
indium oxide to tin oxide is about 20:1.
13. Means according to claim 11, characterized in that the tin
oxide is present as SnO.sub.2 and the indium oxide in several
oxidation stages.
14. Means according to claim 11, characterized in that a
luminescent material layer is disposed on the transparent
electrode.
15. High-dynamic-range position-sensitive radiation detector for
simultaneous optical and electrical acquisition of data
representing incident radiation position comprising
a substrate (20) and
an electrode system (18) which is disposed on a surface of the
substrate and the configuration and arrangement of which permits a
position determination of a charge carrier beam (16) impinging
thereon,
further comprising,
electro-luminescent material (22) deposited on the side of the
electrode system (18) subjected to the charge carrier beam, and
generating optically observable (32,34) indications of impacts
thereon of said charge carrier beam,
and wherein
(a) the electrode system (18) consists of a transparent material,
and generates electrical data representative of the positions of
impacts of charge carriers thereon; and
(b) substrate (20) consists of a transparent material, thereby
permitting visual observation (32,34) through said electrode system
and substrate, of charge carrier impact on said electro-luminescent
material (22).
16. Detector according to claim 15, wherein (FIG. 5) said electrode
system configuration includes wedge-shaped electrodes tapering from
one edge of said electrode system to an opposing edge.
17. Detector according to claim 15, wherein said electrode system
configuration includes wedge-shaped electrodes tapering from one
edge of said electrode system toward a center thereof.
Description
FIELD OF THE INVENTION
The present invention relates to the detection of radiation, in
particular position-sensitive radiation detectors.
DESCRIPTION OF THE RELATED ART
A position-sensitive radiation detector is described in the
publication of C. Martin et al. in Rev. Sci. Instrum. 52 (7), July
1981, 1067-1074. Radiation detectors of the type of interest here
comprise an electrically conductive electrode system which is
arranged on the surface of a substrate and the configuration and
arrangement of which permits determination of the position of an
incident charge carrier beam in two coordinate directions. A known
electrode system of this type includes four electrodes, an
electrode pair having opposing wedge-shaped electrode portions each
tapering towards the other electrode and a second electrode pair
nested in the first and comprising adjacent strip-shaped electrodes
whose widths vary oppositely transversely of their longitudinal
direction. The impingement position of a radiation beam of adequate
cross-section can be determined with this electrode system in two
mutually perpendicular coordinate directions from the ratio of the
charge carrier streams absorbed by the individual electrodes.
Electrode systems of this type also exist which have only three
electrodes and anode arrays in which the position of an impinging
charge carrier beam can be determined in polar coordinates. When
the radiation distribution is optical (electromagnetic) radiation
it is converted as position-true as possible to a corresponding
charge carrier distribution, in particular electron distribution,
which can be done for example by a photocathode and a following
photoelectron multiplier system, e.g. microchannel plates.
Apart from position-sensitive radiation detectors of the
aforementioned type operating with electronic signal acquisition,
the publication of Panitz in J. Vac. Sci. Technol., 17 (3),
May/June 1980, 757, 758 also discloses a position-sensitive
radiation detector operating with optical signal acquisition. In
this optical radiation detector, by the radiation distribution to
be detected, a luminescent layer is stimulated to luminescence and
the resulting optical radiation distribution is converted with a
television camera, for example vidicon camera, to a corresponding
electrical video signal.
Furthermore, position-sensitive radiation detectors exist whose
electrode system consists of a single resistance electrode or an
array of silicon-photoelement segments, cf. for example the
Dissertation by Thomas Schiller, Technical University, Berlin,
1985, p. 30, 31.
A disadvantage of the known radiation detectors is that they do not
permit simultaneous optical and electrical signal acquisition. This
would however for example be desirable when the intensity range of
the radiation to be detected covers several powers of ten or when
in measurements in which small input signal intensities are to be
expected adjustment can be made by visual observation in a
preliminary test with high intensities. Detectors on a silicon
basis have high noise and can only be baked out to a limited
extent. Detectors with resistance electrodes suffer from high
geometrical distortions. The two latter detector types cannot
detect more than 10.sup.6 events per second.
SUMMARY OF THE INVENTION
The main objective of the invention is to provide a
position-sensitive radiation detector which permits at the same
time both an electronic and an optical signal acquisition and is
distinguished by a high dynamic range.
Apart from the possibility of simultaneous electronic and optical
signal acquisition, the radiation detector according to the
invention has the further substantial advantage of a high dynamic
range which extends up to about 10.sup.13 events per second and
more.
A preferred embodiment of the present radiation detector includes a
disc-shaped substrate of optically transparent material,
furthermore an electrode system which is arranged on the major
surface of the substrate and the configuration and arrangement of
which permits a position determination of impinging charge carriers
and which consists according to the invention of optically
transparent material, and a luminescent substance layer which is
arranged on the side of the electrode system facing the charge
carrier source.
The electrode system of the preferred radiation detector comprises
electrodes of a mixture of indium oxide and tin oxide, the ratio of
indium to tin being about 20:1 and the tin oxide being present
solely in the form of SnO.sub.2 while the indium oxide may be
present in all its oxidation stages In.sub.2 0.sub.3 . . . InO.
The layer forming the transparent electrode array may be deposited
chemically from the gas phase by CVD (chemical vapor deposition) or
by a sputtering method as a thin layer.
When the radiation to be detected is electromagnetic radiation it
is converted for example by a photocathode true to position to a
corresponding charge carrier, in particular electron, pattern.
The charge carrier pattern is preferably amplified by a multiplier,
such as a channel plate or other secondary electron multiplier
(SEM) system, before it is incident on the electrode array of the
radiation detector.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinafter examples of embodiment of the invention will be
explained with reference to the drawings, wherein:
FIG. 1 is a schematic illustration of a preferred embodiment of the
position-sensitive radiation detector according to the
invention;
FIG. 2 is a greatly enlarged cross-section through a part of a
detector anode;
FIG. 3 is a plan view of a preferred electrode system for a
detector anode and
FIGS. 4, 5 and 6 are individual view of the three electrodes of the
electrode system of FIG. 3.
p The preferred radiation detector system illustrated schematically
in FIG. 1 includes a sheet-like photocathode 10 for position-true
conversion of an impinging optical radiation distribution
(radiation pattern, image) 12 to a corresponding electron
distribution. The electron distribution is amplified position-true
by a secondary electron multiplier. The secondary electron
multiplier includes in the preferred embodiment illustrated two
microchannel plates connected in series. The amplified electron
distribution 16 is incident onto an electrode system connected as
anode array 18 and arranged on a surface of a substrate 20. The
electrode system 18 includes a plurality of electrodes (see FIG. 3
and the aforementioned publication of Martin et al.) whose
configuration and arrangement permits determination of the position
of an impinging charge carrier beam of adequate cross-section. As
described up till now the radiation detector is known.
According to the invention the substrate 20 consists of an
optically transparent material such as glass. Furthermore, the
electrodes of the electrode system 18 consist of an electrically
conductive and optically transparent material. Also, at least on
the electrodes, preferably on the entire electrode-side surface of
the electrode-substrate array, a layer 22 of luminescent material
(phosphor) is disposed as shown more exactly in FIG. 2. The
luminescent material may consist in known manner of a doped
semiconductor compound such as CdSe:Ag.
The electrodes of the electrode system 18 may consist of a metal,
such as Au, of metal oxides, such as SnO.sub.2, In.sub.2 O.sub.3,
RuO, possibly doped with a non-metal such as fluorine, and
so-called "organic metals" such as polycarbazoles,
polyphenothiazines (doped with iodine), which are transparent in
the form of a thin layer or at least translucent. In the embodiment
preferred at present a mixture of indium oxide and tin oxide is
used, the ratio of indium to tin being about 20:1. The tin oxide is
present solely in the form of SnO.sub.2 whilst the indium oxide may
be present in all the oxidation stages In.sub.2 O.sub.3. . .
InO.
The indium oxide-tin oxide layer may be deposited from the gas
phase by CVD (chemical vapor deposition) or by a sputtering method
in known manner.
The electrode system 18 makes it possible to detect the position
and intensity of impinging electron pulses in known manner by means
of a signal processing unit 24 which furnishes for example a
digital output signal. With the radiation detector according to the
invention however simultaneous optical-electronic signal
acquisition is also possible. For this purpose in the example of
embodiment illustrated in FIG. 1 on the side of the transparent
substrate 20 remote from the electrode system 18 an optoelectronic
image pickup system 26 is disposed which comprises an objective
lens 28, indicated only schematically, and a television camera 30
which for example can operate with a vidicon or a charge-coupled
device (CCD) and furnishes a video signal which represents the
optical radiation distribution generated by the luminescent
material layer 22. Instead of the optical-electronic image pickup
system 26 or additionally thereto means may also be provided for
visual-optical observation and/or photographic recording of the
visible image generated by the luminescent layer 22, for example an
eyepiece 34 and a partially reflecting mirror 36 disposed between
the substrate 20 and the objective 28.
An advantageous electrode system which is known in principle from
the publication of Martin et al.(l.c.) is illustrated in FIGS. 3 to
6. FIG. 3 shows the electrode system as a whole. In FIGS. 4, 5 and
6 the three electrodes 18, 18b and 18c of the electrode system are
shown separately.
The first electrode 18a illustrated in FIG. 4 and comprising a
terminal A consists of a comb-like array of strips with width
decreasing from the left to the right. The second electrode 18b
illustrated in FIG. 5 and having a terminal B includes an array of
identical wedge-shaped electrode portions which extend into the
intermediate spaces between the strips of the electrode 18a.
Between the projecting electrode portions of the electrodes 18a and
18b there is a third meander-shaped electrode 18c which in the
electrode system of FIG. 3 occupies the intermediate space between
the electrodes 18a and 18b and has two terminals C.sub.1, C.sub.2.
The width of the upper, in FIG. 3, substantially V-shaped ends of
the meander winding decreases from the left to the right and in
addition the ratio of the widths of the legs of said windings
changes in the manner shown in FIG. 6.
The invention can of course also be implemented with other
electrode configurations, for example the other electrode
configurations which are described in the aforementioned
publication of Martin et al., and also with a resistance electrode
of the type mentioned at the beginning. It may be applied not only
in position detectors of the type described and mentioned but also
for example in field-ion microscopes, transmission raster
microscopes, X-ray microscopes images converters and amplifiers,
such as night-sight devices, image pickup means for astronomical
purposes, LEED systems (low energy electron diffraction), etc.
* * * * *